Cross-link–induced autophobicity in polymer melts: A re-entrant wetting transition

We have investigated the wetting behaviour of a polymer melt on top of a cross-linked network of itself. For substrate films that were not cross-linked at all (or at very low cross-link densities) the melt completely wets the underlying layer. At intermediate cross-linking densities we observe dewetting, which we suggest is due to the brush-like surface of the network. At higher cross-linking densities the melt again completely wets the network, due, we believe, to increased roughening of the surface of the cross-linked substrate

Transferable thin films of mesoporous silica

Synthesis of supported and free-standing thin mesoporous silica films from solution was investigated. It has been reported that the initial reactant concentration as well as the nature of the substrate affect the structure and symmetry of the resulting films. We found that by preparing the films on a polymer-coated substrate, one could de-couple the two parameters and control the structure of the resulting film exclusively via the concentration of reactants in solution. In addition, dissolution of the polymer layer in an organic solvent resulted in free-standing films, of hexagonal (MCM 41) or lamellar mesoporous phases, that could be transferred onto a target substrate. Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) measurements were employed to characterize the films

Modélisation et commande floues de type Takagi-Sugeno appliquées à un bioprocédé de traitement des eaux usées

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

van der Waals stable thin liquid films: Correlated undulations and ultimate dewetting

The evolution of pre-rupture undulations at the liquid-air interface of thin non-wetting liquid films spread on a solid substrate was monitored in real time by non-perturbative interference microscopy. The spatial distribution of the incipient undulations is non-random and characterized by a typical wavelength, as predicted for van der Waals unstable films, despite the fact that the system is expected to be vdW-stable, and that ultimate dewetting of films appears to take place via a heterogeneous nucleation mechanism

Effect of interfaces on the crystallization behavior of PDMS

The reversible thermal behavior of a non-entangled semicrystalline polymer, poly(dimethylsiloxane), PDMS, was investigated in the presence of sub-micron particles. Filled polymer systems of this type are characterized by a large surface-to-volume ratio but lack the external confinement that is typical for a thin film geometry. Differential-scanning calorimetry (DSC) measurements indicate that the presence of the nanometric solid additives enhances the crystallization rate as compared to native PDMS melts. Different types of additives and surface interactions resulted in a similar effect, suggesting that the origin of the enhanced crystallinity is non-specific. The effect is attributed to entropic interactions in the boundary layer

Quasi-one dimensional in-plane conductivity in filamentary films of PEDOT:PSS

The mechanism and magnitude of the in-plane conductivity of poly(3,4-ethy-lenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin films is determined using temperature dependent conductivity measurements for various PEDOT:PSS weight ratios with and without a high boiling solvent (HBS). Without the HBS the in-plane conductivity of PEDOT:PSS is lower and for all studied weight ratios well described by the relation with T0 a characteristic temperature. The exponent 0.5 indicates quasi-one dimensional (quasi-1D) variable range hopping (VRH). The conductivity prefactor s0 varies over three orders of magnitudes and follows a power law s0¿c3.5PEDOT with cPEDOT the weight fraction of PEDOT in PEDOT:PSS. The field dependent conductivity is consistent with quasi-1D VRH. Combined, these observations suggest that conductance takes place via a percolating network of quasi-1D filaments. Using transmission electron microscopy (TEM) filamentary structures are observed in vitrified dispersions and dried films. For PEDOT:PSS films with HBS, the conductivity also exhibits quasi-1D VRH behavior when the temperature is less than 200 K. The low characteristic temperature T0 indicates that HBS-treated films are close to the critical regime between a metal and an insulator. In this case, the conductivity prefactor scales linearly with cPEDOT, indicating the conduction is no longer limited by a percolation of filaments. The lack of observable changes in TEM upon processing with the HBS suggests that the changes in conductivity are due to a smaller spread in the conductivities of individual filaments, or a higher probability for neighboring filaments to be connected rather than being caused by major morphological modification of the material